The present invention relates generally to an image-pickup apparatus, and more particularly, to an image-pickup apparatus including a focus detection apparatus which detects the focusing state of an image-pickup optical system. The present invention is preferable for use in a camera and a video camera, for example.
With the widespread use of image-pickup apparatuses typified by a digital camera and a video camera, a higher level of quality and a smaller size are increasingly needed in such image-pickup apparatuses. Particularly, a higher degree of accuracy and a reduced size are required in a focus detection apparatus which detects the focusing state of an image-pickup lens (image-pickup optical system) in an image-pickup apparatus. In recent years, focus detection apparatuses operate predominantly with a TTL phase difference detection method in which the pupil of an image-pickup lens is split into a plurality of areas, luminous fluxes pass through the respective areas and form a plurality of images, and the relative positional relationship between the images is used to detect the focusing state of the image-pickup lens (for example, see Japanese Patent Laid-Open No. S62 (1987)-95511, Japanese Patent Laid-Open No. H09 (1997)-184965, and Japanese Patent Laid-Open No. 2003-107323).
Japanese Patent Laid-Open No. S62 (1987)-95511 has disclosed a focus detection apparatus which uses a focus detection point (cross focus detection point) allowing focus detection in a plurality of directions to ensure high focus detection performance regardless of the spatial pattern of an object. Japanese Patent Laid-Open No. H09 (1997)-184965 and Japanese Patent Laid-Open No. 2003-107323 have disclosed a focus detection apparatus which uses a plurality of focus detection points allowing focus detection in a plurality of directions to ensure high focus detection performance over a wide area within an image-pickup region. Especially, the focus detection apparatus disclosed in 2003-107323 includes a plurality of focus detection optical systems (that is, including a plurality of apertures, image-reforming optical systems, and photoelectrical conversion elements) to realize a number of cross focus detection points placed in the image-pickup region.
The focus detection apparatus disclosed in Japanese Patent Laid-Open No. 2003-107323, however, includes many cross focus detection points placed in the image-pickup region, so that the number of components (that is, members constituting the focus detection optical systems) is increased to cause a higher cost and a larger size of the focus detection apparatus.
On the other hand, focus detection with any type of interchangeable lens (image-pickup lens) in an image-pickup apparatus can be performed by eliminating vignetting due to the entrance pupil and the exit pupil of the image-pickup lens. However, to use a number of interchangeable lenses and dispose many cross focus detection points within the image-pickup region, luminous fluxes (optical images) after passing through the associated apertures should not overlap on a light-receiving element (photoelectrical conversion element). The prevention of overlapping of the optical images on the light-receiving element requires a longer optical path of a focus detection optical system or refraction of a luminous flux by an optical member, which leads to an increased size of the focus detection apparatus and a higher cost due to an increased number of optical members.
To place a number of cross focus detection points, a number of arrays of sensors need to be disposed on the light-receiving element, resulting in an increased size of a sensor chip and a higher cost.